This is a 12VDC to 9VDC Converter circuit. You may use this circuit if you have fixed 12V power supply / battery, but you need 9V power supply for your electronic devices.
Component Part List:
R1________ 560 ohm C1________ 1000μF/16V, Electrolytic C2________ 100μF/16V, Electrolytic C3________ 330nF, Ceramic Z1________ 9.1V, 0.4watt zener Q1________ ECG184, NTE184
To get a more precise output voltage, replace zener diode Z1 with 10V and R1 with a 1 Kilo ohm potentiometer.
A Coolrib for Q1 is optional. Simple circuit to power your 9 volt cassette recorder and other stuff.